- Runs at a lower voltage and clock speed -- This reduces heat output and power consumption but slows the processor down. Most laptops also run at a higher voltage and clock speed when plugged in, and at lower settings when using the battery.
- Mounts to the motherboard without using pins -- Pins and sockets take up a lot of room in desktop PCs. Some motherboard processors mount directly to the motherboard without the use of a socket. Others use a Micro-FCBGA (Flip Chip Ball Grid Array), which uses balls instead of pins. These designs save space, but in some cases mean that the processor cannot be removed from the motherboard for replacement or upgrading.
- Has a sleep or slow-down mode -- The computer and the operating system work together to reduce the CPU speed when the computer is not in use or when the processor does not need to run as quickly. The Apple G4 processor also prioritizes data to minimize battery drain.
Some laptops use desktop CPUs that are set to run at lower clock speeds. Although this can improve performance, these laptops typically run much hotter and have a significantly reduced battery life.
Laptops usually have small fans, heat sinks, heat spreaders or heat pipes to help dissipate the heat from the CPU. Some higher end laptop models reduce heat even further with liquid coolant kept in channels alongside the heat pipe. Also, most laptop CPUs are near the edge of the unit. This allows the fan to move the heat directly to the outside instead of across other components.
Source : http://www.howstuffworks.com/
In a way, the skyrocketing popularity of laptop computers is ironic. They're completely portable, and they use less power and make less noise than desktop models. But, they're often a little slower and have less graphics and sound processing power, although these differences can be too small for most users to notice.
Laptops are also more expensive than desktops. The price gap is closing, though -- laptop prices are falling faster than desktop prices, and laptop PCs actually outsold desktop models for the first time in May of 2005 [Source: Windows IT Pro].
How can all the equipment found in a desktop tower fit into such a small package? And how can laptops be efficient enough to run on battery power alone? In this article, you'll discover the answers to these and other questions about laptops.
Overall, laptop and desktop computers are very similar. They have the same basic hardware, software and operating systems. The primary difference is how their components fit together.
A desktop computer includes a motherboard, video card, hard drive and other components in a large case. The monitor, keyboard, and other peripherals connect wirelessly or with cables. Whether the case sits vertically or horizontally, it has lots of space for add-in cards, cables and air circulation.
A laptop, however, is much smaller and lighter than even the most compact PC tower. Its screen is an integrated part of the unit, as is its keyboard. Instead of a spacious case with lots of room for air circulation, a laptop uses a small, flat design in which all the pieces fit together snugly.
Because of this fundamental design difference and because of a laptop's inherent portability, components have to:
- Fit into a compact space
- Conserve power
- Produce less heat than desktop components
Often, these differences make the components more expensive, which can contribute to higher laptop prices.
Source : http://www.howstuffworks.com/